at 5 lbs you're not going to be able to get much of a glide. the plane sans engine will be 4 lbs... that's a wing loading of 34 oz/sqft which means you'll pretty much have a glide ratio of a cow. plus with 9 lbs on the wings, they will likely collapse under the weight (or rather over it).

and so much for propulsion, that car doesn't have 4-wheel drive and the engine is transversely mounted. will be near impossible to get that to a prop without significant cost and additional weight.

and... saw the avistar fuselage (remains) but didn't see the wing.

from the looks of it, it will be a very difficult project due to the center of gravity of the car being just forward the engine. don't know how you would be able to get all the wings etc mounted. you'd essentially have to build a new frame above the car and hope the engine doesn't burn through it.

the better solution would be to make this a canard meaning that the main wing is in the back rather than in the front and the elevator is in the front. this way the CG needs to be 1/3 the distance from main wing to the stab which means that the car fits right in.